The present invention relates to medical prostheses and, more particularly, to intraluminal medical stents.
Medical stents are used within the body to restore or maintain the patency of a body lumen. Blood vessels, for example, can become obstructed due to plaque or tumors that restrict the passage of blood. A stent typically has a tubular structure defining an inner channel that accommodates flow within the body lumen. The outer walls of the stent engage the inner walls of the body lumen. Positioning of a stent within an affected area can help prevent further occlusion of the body lumen and permit continued flow.
A stent typically is deployed by percutaneous insertion of a catheter or guide wire that carries the stent. The stent ordinarily has an expandable structure. Upon delivery to the desired site, the stent can be expanded with a balloon mounted on the catheter. Alternatively, the stent may have a biased or elastic structure that is held within a sheath or other restraint in a compressed state. The stent expands voluntarily when the restraint is removed. In either case, the walls of the stent expand to engage the inner wall of the body lumen, and generally fix the stent in a desired position.
The present invention is directed to a multi-section stent. The stent incorporates a connecting structure that permits the multiple sections to move relative to another, promoting flexibility and conformance of the stent to a body lumen. For deployment and positioning, the connecting structure holds the stent sections substantially stationary relative to one another. Following deployment, however, the connecting structure allows the multiple stent sections to move relative to one another.
The connecting structure can be made to separate or relax such that the stent sections are able to move relative to one another. The connecting structure can be made to separate or relax by the use of a material that breaks or degrades. Movement of the stent sections may refer to axial movement, lateral movement, tilting, pivoting, rotation, and the like, all of which promote flexibility of the overall stent structure.
Movable stent sections enable flexure of the stent upon deployment within a body lumen. This flexing structure allows better conformance of the stent to the shape of the body lumen, and exerts less overall pressure against the lumen wall, reducing the potential for trauma. Following separation or relaxation of the connecting structure, the multiple stent sections may be completely detached from one another. Alternatively, the stent sections may remain partially connected in a manner that allows substantial independent movement.
The connecting structure can be manufactured to separate, e.g., by breakage, tearing, rupture, etc., thereby disconnecting at least portions of adjacent stent sections to allow increased flexibility. Alternatively, the separable connecting structure can be made from a degradable material that dissolves or otherwise degrades within the body lumen. As a further alternative, the connecting structure may connect the stent sections in a non-rigid manner, allowing movement while retaining interconnection between the stent sections. In any of the above cases, adjacent stent sections become more movable relative to one another, allowing the stent to flex and adapt to the body lumen. Each of the individual stent sections may settle into a substantially fixed position, however, and heal into the luminal wall.
A separable connecting structure can be made responsive to intra-luminal forces or external forces applied upon deployment. To promote separation by breakage, a continuous stent structure can be weakened, e.g., by thinning, perforation, scribing, or pre-stressing, at selected intervals along the length of the stent. Alternatively, discrete connecting members can be formed between stent sections to provide a series of connected stent sections. The connecting members are manufactured to separate under intraluminal forces, thereby disconnecting the stent sections. To promote early separation or breakage, the deployment technique may involve forcibly breaking at least some of the connecting members. In many cases, however, gradual separation or breakage under intraluminal forces will be sufficient.
A connecting structure incorporating a degradable material can be selected to dissolve within the body fluids present within the body lumen in which the stent is positioned. Early degradation can be promoted by pretreating the material, e.g., with a solvent, just prior to deployment. Also, an agent may be introduced into the body to accelerate degradation. If the connecting structure comprises a collagen coating, for example, an enzyme dosage can be administered to the patient to promote degradation. Gradual degradation will be sufficient in most applications, however, simplifying preparation. With degradable materials, therapeutic substances can be added for release into the body lumen as the materials degrade.
As an alternative, the stent can be covered with a brittle or degradable laminating coat that covers at least a portion of the stent, forming a housing for the stent sections. This housing can provide a substantially rigid but separable interconnection of the stent sections. Upon deployment, the housing breaks or degrades to permit greater flexibility among the stent sections. Another alternative is the use of a housing in the form of a breakable or degradable netting or cage that holds the sections together. Upon deployment, the netting or cage can be made to break or degrade, and thereby release the stent sections relative to one another.
Separable connecting portions, whether degradable or breakable, can be selected and manufactured to minimize the risk of releasing larger particles or fragments into the body lumen that could lead to embolism or other serious problems. The stent sections may be completely separated, i.e., disconnected, following breakage of the connecting structure, forming a series of discrete stent sections that extend along the body lumen. Alternatively, the stent sections may remain partially connected, but still provide improved flexibility. For example, material joining adjacent stent sections may remain partially intact to allow flexibility but limit movement.
As further alternatives, the stent sections can be connected with interlocking links, such as loops or chain-links, that allow the stent sections to move, but serve to restrict the overall extent of movement. In some embodiments, the interlocking links may overlap, with degradable or breakable material filling the overlap area to hold adjacent stent sections in a substantially fixed manner and at a substantially fixed distance relative to one another. Following degradation or breakage of the material in the overlap, the links allow at least some degree of movement of the stent sections. In this manner, the length of the stent may increase following deployment, and occupy a greater extent within the body lumen.
In one embodiment, the present invention provides a stent comprising a first stent section, a second stent section, and a connecting structure that connects the first and second stent sections, the connecting structure allowing the first and second stent sections to move relative to one another upon deployment of the stent within a body lumen.
In another embodiment, the present invention provides a stent comprising a first stent section, a second stent section, a first link extending from the first stent section, a second link extending from the second stent section, wherein the first and second links interlock and define an overlap region, and a material formed in the overlap region to hold the first and second stent sections in a substantially fixed relationship, wherein the material is separable upon deployment of the stent within a body lumen, thereby enabling the first and second stent sections to move relative to one another.
In a further embodiment, the present invention provides a stent comprising a first stent section, a second stent section, a first link that interlocks with a second link in the first stent section and a third link in the second stent sections, thereby connecting the first and second stent sections, wherein the first link defines a first overlap region with the second link and a second overlap region with the third link, and a material formed in the first and second overlap regions to hold the first and second stent sections in a substantially fixed relationship, wherein the material is separable upon deployment of the stent within a body lumen, thereby enabling the first and second stent sections to move relative to one another.
In an added embodiment, the present invention provides a stent comprising a first stent section, a second stent section, and a connecting member that connects the first and second stent sections, the connecting member holding the first and second stent sections in a substantially fixed relationship, wherein the connecting member relaxes the connection between the first and second stent sections following deployment of the stent within a body lumen, thereby enabling flexure of the stent.
In another embodiment, the present invention provides a stent comprising a first stent section including a first spring coil, a second stent section including a second spring coil, a first spring arm extending from the first stent section, a second spring arm extending from the second stent section, and a material that connects the first and second spring arms, the material being breakable, thereby at least partially disconnecting the first and second stent sections and allowing the first and second stent sections to move relative to one another.
In a further embodiment, the present invention provides a stent comprising a first stent section, a second stent section, and a housing that encloses at least portions of the first and second stent sections, wherein the housing is breakable upon deployment, thereby allowing the stent sections to move relative to one another following degradation of the housing.
In another embodiment, the present invention provides a stent comprising a first stent section, a second stent section, and a housing that encloses at least portions of the first and second stent sections, wherein the housing is degradable upon deployment, thereby allowing the stent sections to move relative to one another following degradation of the housing.
In another embodiment, the present invention provides a stent comprising a first stent section, a second stent section, and at least one connecting member having a first end attached to the first stent section, a second end attached to the second stent section and a physically separable portion. The physically separable portion may comprise at least one groove in the connecting member. The groove may be formed adjacent to the first end, or adjacent to the first end and the second end.
The connecting member of the stent may further include an angled portion. The angled portion may include a groove and the physically separable portion may comprise the groove. The angle may be less than 45xc2x0, between 45xc2x0 and 135xc2x0, and/or between 135xc2x0 and 180xc2x0.
The stent may include one, two, three, four, or more connecting members. If there are two connecting members, each connecting member may include a first end attached to the first stent section and a second end attached to the second stent section, and the first end of the first stent is adjacent to the first end of the second stent. The first end of the first connecting member and the first end of the second connecting member may be separated by approximately 180xc2x0. The second end of the first connecting member and the second end of the second connecting member may be separated by approximately 180xc2x0. In the stent, the physically separable portion may separate during a deployment of the stent or after a deployment of the stent.
In another embodiment, the stent includes a first stent section, a second stent section; and a pair of connecting members. The connecting members are positioned between the stent sections and connect the stent sections. Each connecting member is substantially coplanar over a portion of a length of the connecting member with the at least one stent section and includes a first end attached to the first stent section, a second end attached to the second stent section and a physically separable portion.
In the stent, the physically separable portion of a first connecting member may be configured to separate from the first stent section and the physically separable portion of the second connecting member may be configured to separate from the second stent section, whereby the first connecting member is configured to reduce tumbling of the first stent section and the second connecting member is configured to reduce tumbling of the second stent section. The stent may be fabricated by electron discharge machining.